Hydraulic underwater sound transducer



Aug. 6, 1963 C. A. CLARK HYDRAULIC UNDERWATER SOUND TRANSDUCER Filed May 22, 1959 FLUID PUMP H l G H SPEED VALVE TRANSDUCER (IJOMPRESSED GAS SUPPLY INVENTOR CHESTER A. CLARK ATTORNEY United States Patent Ofifice 3,10%,022 Patented Aug. 6, 1963 3,100,022 HYDRAULIG UNDERWATER SGUND TRANSDUCER Chester A. Clark, Waldorf, Md, assignor to the United States of America as represented by the Secretary of the Navy Filed May 22, 1959, Ser. No. 815,234 3 Claims. (til. 181--.5) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to underwater sound transducers and particularly to hydraulically driven transducers.

The field of low frequency underwater transducers is of current interest because of the greater range obtainable in this portion of sound spectrum. The lower frequencies,

i.e., below one kilocycle, also permit the use of purely mechanical sources, which are capable of producing large amounts of audio power with great efliciency.

An object of the present invention is, therefore, to provide a compact and efficient hydraulic transducer for underwater use.

A further object of the invention is to provide an underwater sound transducer which is particularly useful with water craft.

These and other objects of the invention will be better understood with reference to the accompanying drawing 3 wherein FIG. 1 shows a front view of the transducer with the front piston and diaphragm removed;

FIG. 2 shows a side section view of the transducer taken along section line A-A; and

FIG. 3 shows a typical system for utilizing the transducer of the present invention.

Referring to FIGS. 1 and 2 the transducer comprises a central banjo-shaped body portion 11 and a pair of diaphragms "12 and 13. The center of the body includes an axial aperture 14 which acts as a fiuid passageway. The end portions of aperture 14 are enlarged to provide a pair of hydraulic cylinders 15. The center of each diaphragm includes a raised hub portion 16 which fits snugly but slidably within one of the enlarged portions of the central aperture of the body and serves as a hydraulic piston. When fluid is forced into the central aperture, the pistons slide axially as indicated by the arrows in FIG. 2.

The body is composed mainly of an essentially discshaped solid 17 of revolution to which is attached a stem 18. It should be understood, however, that the body may be a wafer-shaped structure of any shape, e.g., square or rectangular, as suits the method of manufacture and the particular application. The stem terminates in a flange 19' designed for mounting the transducer on an underwater surface, such as the outer surface of a ships hull. The overall shape of the transducer is such that a minimum resistance to motion in an external medium is encountered when the device is properly oriented.

A first fluid passageway 20 is provided through the flange 19, stem 18 and disc-shaped solid portion 17 of the body to feed fluid to or from the central aperture 14. A pipe coupling 21 is connected to the open end of the passageway to facilitate the connection of a feedline from a hydraulic sound generator. The inner corner in each of the enlaged portions of the central aperture is relieved to provide a discharge annulus 22. A second fluid passageway 23 is provided between the discharge annulus and the exterior of the transducer substantially parallel to the first passageway. It may be necessary to drill through the body normal to this second passageway to interconnect it with the discharge annulus. A coupling 24 similar to coupling 21 is provided at the flange end of the second passageway.

The diaphragms 12 and 13 are also wafer-shaped and substantially equal in outside diameter to the solid of revolution 17 in the body. The periphery of each diaphragm is formed as a rigid flange which is sealed in an airtight fashion to the periphery of the solid of revolution. For this purpose suitable gaskets 25 are placed between the mating surfaces of the diaphragms and the body and the former secured to the latter by means of a plurality of screws 26. If disassembly is not contemplated, the mating surfaces may be welded or soldered.

A chamber 27 is thus provided between the body and each diaphragm. These chambers are filled with gas which does not appreciably load the back faces of the diaphragrns. Each piston may be provided with a number of resilient rings 23 of metal or plastic to prevent the fluid from leaking into the gas filled chambers. An additional scavenging passageway is provided through the body and stem with an end opening into the bottom of each of the gas filled chambers. The flange end of this passageway may be provided with a pipe coupling, not shown, similar to the couplings 21 and 24-. Any hydraulic fluid which leaks past the pistons may thus be removed through this passageway.

A fourth passageway 30 is provided with an open end at the top of the gas filled chambers to admit gas under pressure. A small passageway 31 through the body allows free circulation of gas into both the chambers. The pressure on the back faces of the diaphragms may thus be made to balance out the external pressure encountered when the transducer is used at great depths. The compressed gas also serves as a means to drive out any accumulated hydraulic fluid in the bottom of the charm bers through the scavenging passageway.

The structure of the transducer makes it extremely simple to fabricate. The body and diaphragrns are quickly formed by a drop forge, with little or no machining necessary. All of the passageways including the scavenging passageway are formed by simple drilling operations. The latter is first drill-ed entirely through the body sufficiently off-center to miss central passageway. The drill is then inserted in the lower end of the portion thus formed, and aligned in turn with the lowest point in each chamber to complete the drilling operation. The lower end is then plugged externally with solder or other suitable sealing means. A suitable material for the body is aluminum.

FIG. 3 shows the transducer employed. in a system. The system employs a pump 40 which urges a fluid into a high speed valve assembly 41 through path 42. A first valve in the assembly opens periodically to transmit the fluid in pulses through a second path 43 to the transducer. The second path is connected to the flange end of the passageway 20 in FIG. 1. The passageway 23 in FIG. 1 from the discharge annulus is connected by fluid path 44- in FIG. 3 to a second valve in the assembly. The second valve is open only between the open periods of the first valve. Fluid from the annulus returns to the pump through path 45 for recirculation. A compressed gas supply '46 is connected to passageway '30 of FIG. 1 through gas line 47, as shown in FIG. 3, to apply the necessary pressure within the gas chambers of the transducer. Any accumulated fluid in the gas chambers which is forced out of the passageway 29 in FIG. 1 is transmitted through the scavenging line 48 in FIG. 3 to the pump. Alternatively, the scavenged fluid may be discarded, if desired.

Many variations of the basic structure disclosed above are possible. The gas compressor and/ or the scavenging line may be omitted along with the associated passageways in the transducer, when fluid leakage or external diaphragm pressure can be neglected. The pump and high speed valve may be interdependent parts of a single unit. The transducer may also be operated by steam or compressed air.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. An underwater sound transducer comprising, a substantially disc-shaped body having an axis of circular symmetry, said body including a radial stem attached to the outer edge thereof, first and second substantially discshaped diaphragms axially aligned with said disc-shaped body, said body being centered between said diaphragms, said body having a first centrally located axial fluid passageway therein, each of said diaphragms having a centrally located projection extending into and closing opposite ends of said passageway, a second fluid passageway extending through said stem and said body intersecting said first passageway between said projections, and airtight sealing means joining the peripheries of said diaphragms to said disc-shaped body.

2. An underwater sound transducer comprising, a thin substantially flat wafer-shaped body portion defining a pair of closely spaced substantially parallel broad faces and a peripheral edge, said body including a first passageway through the center thereof normal to said broad faces, a pair of thin substantially flat wafer-shaped diaphragms arranged parallel to said broad faces with said body separating said diaphragms, each said diaphragm including a peripheral edge, the thickness of said body and diaphragms being greater than average at said peripheral edges, said peripheral edges being hermetically sealed together to define an interior chamber, a raised hub centrally mounted on each diaphragm and extending into said passageway, each said hub closing the adjacent end of said first passageway and presenting an end face within said passageway, and a second passageway within said body extending from said first passageway between said end faces through said peripheral edge of said body.

3. An underwater sound transducer comprising, a thin substantially flat wafer-shaped body portion defining a pair of closely spaced substantially parallel broad faces and a peripheral edge, saidbody including a first passageway through the center thereof normal to said broad faces, a pair of thin substantially fiat wafer-shaped diaphragms arranged parallel to said broad faces with said body separating said diaphragms, each said diaphragm including a peripheral edge, the thicknesses of said body and diaphragms being greater than average at said peripheral edges, said peripheral edges being hermetically sealed together to define an interior chamber, a raised hub cen trally mounted on each diaphragm and extending into said passageway, each said hub closing the adjacent end of said first passageway and presenting an end face within said passageway, a second passageway within said body extending from said first passageway between said end faces through said peripheral edge of said body, a third passageway within said first passageway between said end faces through said peripheral edge of said body and valve means to alternately block fiuid flow in said second and third passageway.

References Cited in the file of this patent UNITED STATES PATENTS 1,409,341 Harrison Mar. 14, 1922 2,587,848 Horsley et al. Mar. 4, 1952 2,804,042 Gavreau Aug. 27, 1957 

1. AN UNDERWATER SOUND TRANSDUCER COMPRISING, A SUBSTANTIALLY DISC-SHAPED BODY HAVING AN AXIS OF CIRCULAR SYMMETRY, SAID BODY INCLUDING A RADIAL STEM ATTACHED TO THE OUTER EDGE THEREOF, FIRST AND SECOND SUBSTANTIALLY DISCSHAPED DIAPHRAGMS AXIALLY ALIGNED WITH SAID DISC-SHAPED BODY, SAID BODY BEING CENTERED BETWEEN SAID DIAPHRAGMS, SAID BODY HAVING A FIRST CENTRALLY LOCATED AXIAL FLUID PASSAGEWAY THEREIN, EACH OF SAID DIAPHRAGMS HAVING A CENTRALLY LOCATED PROJECTION EXTENDING INTO AND CLOSING OPPOSITE ENDS OF SAID PASSAGEWAY, A SECOND FLUID PASSAGEWAY EXTENDING THROUGH SAID STEM AND SAID BODY INTERSECTING SAID FIRST PASSAGEWAY BETWEEN SAID PROJECTIONS, AND AIRTIGHT SEALING MEANS JOINING THE PERIPHERIES OF SAID DIAPHRAGMS TO SAID DISC-SHAPED BODY. 